How should I convert GML to geojson data using ogr2ogr. I used :
ogr2ogr -f "GeoJSON" bd.geojson bd.gml
But in this case I have only part of my data , not all. I tried add -append , but it didn't work properly.
It's hard to say for sure what the issue is based on your question, but you could try to use the
-nlt flag (from documentation http://www.gdal.org/ogr2ogr.html). This will (explicitly) specify the output geometry type. Since you have mixed geometry you might try the command
ogr2ogr -f "GeoJSON" -nlt "GEOMETRYCOLLECTION" bd.geojson bd.gml